The Champions League gets all of the buzz, but the side door into that competition also resumes this week.

The Europa League starts its knockout phase today, and some big-name clubs will be looking to keep their chances of winning this tournament — and a spot in next season’s Champions League — alive.

These are two-legged ties, with the return matches set for next week. Here are some fixtures of interest:

Midtjylland vs. Manchester United — Wayne Rooney is set to miss this match because of a knee injury, joining Matteo Darmian and Cameron Borthwick-Jackson on the injury list. United is bringing several young players for this trip, and we may see more than one first-team debut.

The Danes, currently sitting third in the Superliga table, will be looking to take advantage and put themselves in a good position for the return leg at Old Trafford. This is the deepest Midtjylland has ever advanced in a European competition.

Fiorentina vs. Tottenham Hotspur — Spurs face the age-old question: Should they go all out in this competition, or focus on winning the Premier League title. And where does the FA Cup run fit in?

These are the choices Mauricio Pochettino must make with a cup match with Crystal Palace looming on Sunday. Tottenham, in fact, has four matches on the schedule in the next 10 days. A little squad rotation has to be coming somewhere along the line.

The Italians are facing a similar dilemma, sitting third in the Serie A table. Fiorentina faces a league visit to Atalanta on Sunday, and may also have to make some tough choices in its lineup.

There’s also a bit of a revenge factor in play, as the Viola knocked Spurs out of this competition last season.